The present invention relates to an apparatus for tissue treatment, such as for hair removal and for photocoagulation of veins.
It is known to utilise laser light for tissue treatment, such as cosmetic tissue treatment, such as dermal ablation, removal of hair, photocoagulation of veins, etc.
Hair removal may be effected by directing a laser beam at a hair follicle to destroy the hair follicle and its adjacent blood vessels by the heat produced by photothermolysis.
Furthermore, coagulation of veins may be effected by directing a laser beam at the veins to coagulate the blood in the veins.
During treatment of tissue, such as an epidermal layer, hair, veins, etc, it is essential not to damage underlying or surrounding tissue. Residual heat may cause untreated cells to char and become necrotic, whereby scars may be formed. Thus, it is desirable to apply laser power only to tissue to be treated and only for a short time, to minimise transmission of conducted heat to underlying and surrounding tissue.
To some extend this has been obtained by selective photothermolysis, i.e. laser light is utilised having a wavelength that is selectively absorbed by tissue to be treated and that is not absorbed by the surrounding and healthy tissue. The selective absorption of the laser light causes selective photothermolysis in the tissue to be treated.
Light of a wavelength that is absorbed in a hair follicle and its adjacent blood vessels will be scattered in all directions when propagating from a tissue surface down to the hair follicle to be destroyed by the heat produced by photothermolysis. Therefore, it is required to illuminate a rather large spot on the tissue surface above the hair follicle(s) to be destroyed in order to increase the probability of photons being scattered in direction of the hair follicle(s). Simultaneously, the power of the illuminating light beam must be sufficient for enough heat to be generated to destroy the hair follicle and its adjacent blood vessels.
In the art this has lead to bulky hair depilators with high power lasers producing a spot size of 10 mm or more.
Throughout the present description the term spot size means the diameter of the spot in question.
It is an object of the present invention to provide an apparatus for hair removal that is adapted to automatically and accurately destroy hair follicles without damaging surrounding tissue.
It is another object of the present invention to provide an apparatus for hair removal that is adapted to remove hair from a large area of a patient.
It is a further object of the present invention to provide an apparatus for hair removal, having a handpiece that can be moved around, i.e. traversed and rotated, freely by an operator, i.e. without exerting forces acting against the movement.
According to a first aspect of the invention, the above-mentioned and other objects are fulfilled by an apparatus for tissue treatment comprising a light emitter for emission of a first light beam, movable first deflecting means for deflection of the first light beam into a treating light beam, an output for emission of the treating light beam towards a target surface and illuminating a spot on the target surface, first moving means for moving the first deflecting means, and first deflecting control means for controlling the first moving means and being adapted to control the first moving means so that the treating light beam traverses a target surface area stepwise with steps that are greater than half the diameter of the spot.
According to a second aspect of the invention, a handpiece is also provided, comprising an input connector for connection of a first beam-outlet end of a first optical fibre to the handpiece and for alignment of the first optical fibre with an axis of the handpiece so that a first light beam emitted from the first beam-outlet end is transmitted substantially along to the axis, movable first deflecting means for deflection of the first light beam into a treating light beam, an output for emission of the treating light beam towards a target surface and illuminating a spot on the target surface, first moving means for moving the first deflecting means, and first deflecting control means for controlling the first moving means and being adapted to control the first moving means so that the treating light beam traverses a target surface area stepwise with steps that are greater than half the diameter of the spot.
When the handpiece is kept in a fixed position in relation to a target surface that is illuminated by the treating light beam changing of the position of the deflecting means causes the treating light beam to traverse or scan the target surface along a curve. An area may be traversed or scanned by the treating light beam, e.g. by letting the treating light beam traverse or scan a meander like curve substantially covering the area or, by traversing or scanning the area line by line. In the present context, the type, number and shape of curves traversed by the treating light beam in order to traverse a specific area is denoted the traversing pattern or the scan pattern. The area that is scanned or traversed by the treating light beam is denoted the scan area, the treatment area or the traversed area. The scanning may be performed stepwise as further explained below.
In the art, it has hiterto been recognised that efficiency of hair removal can be increased by increasing spot size and laser power. However, it has surprisingly been found by the present inventors that a smaller spot size and a low power laser can lead to effective hair removal so that an apparatus for hair removal that is not bulky and expensive is provided according to the present invention.
According to the present invention, an apparatus for tissue treatment illuminating a spot size ranging from 1 to 9 mm, preferably from 2 to 8 mm, more preferred from 2 to 6 mm, most preferred approximately 4 mm, is provided.
It is further preferred that the output power of the diode laser is less than 250 W, preferably less than 175 W, more preferably less than 125 W, most preferred approximately 80 W.
In order to distribute energy uniformly across tissue to be treated, it is preferred to scan the tissue along a curve in steps whereby the illuminated spot is allowed to stay in a specific treating position 40-100 ms, such as 60-100 ms, preferably approximately 80 ms, followed by movement of the spot to the next treating position within a few milliseconds. Preferably, the centre to centre distance between two succeeding spot positions is less than a spot diameter, such as between half a spot diameter and a diameter of the spot, preferably such as approximately half a spot diameter, most preferred such as two thirds a spot diameter, so as to provide for a controlled overlap of the spots resulting in an effective hair removal. The thus implied overlap ensures a uniform distribution of energy across the traversed tissue area, and thus a uniform removal of hairs. It is further preferred to scan the tissue area line by line scanned successively in the same directions having a spot overlap such as mentioned above.
However, the treating light beam traverses a line to be treated a first time and a second time stepwise with a step size being substantially greater than the diameter of the spot. The centre to centre distance between two succeeding treating spot positions may be thus be larger than a spot diameter, such as 1.5 times a spot diameter, preferably such as approx. four thirds a spot diameter, and still provide effective hair removal. The scanning may be performed so that the first traversing of the treating light beam illuminates a first sequence of spots and the second traversing of the treating light beam illuminates a second sequence of spots in the same line, the distance between the first illuminated spot in the first sequence and the first illuminated spot in the second sequence being substantially equal to half the size of the steps between succeeding illuminated spots in the first sequence. The scanning may thus be performed so that after treatment of succeeding treating spots in a scan line, the line is scanned again so that the areas, the intermediate spots, not having received treatment in the first scan due to the large distance between two succeeding spots are now treated so as to obtain an overlap as mentioned above. It may then be preferred to scan the tissue area along a curve constituted by lines scanned successively in the same direction having a spot overlap such as mentioned above.
When scanning the tissue area along a curve constituted by lines scanned successively in the same or in opposite directions it is preferred that during traversing, treating spots on adjacent lines are positioned so that spot centres on one line are positioned in between spot centres on an adjacent line, whereby spot overlap as mentioned above is also obtained from one line to adjacent lines.
Alternatively, to optimise the scanning sequence the centre to centre the distance between two succeeding treating spot positions may be equal to approximately the diameter of the spot. Thus, treating spot centres are positioned as spot centres would be for hexagonal spots abutting each other.
Hair follicles and blood in blood vessels selectively absorb light energy of certain wavelengths. Thus, it is preferred to use light sources, such as lasers, generating light at wavelengths with a selective high absorption in hair follicles and preferably also in blood, preferably wavelengths larger than 190 nm, such as wavelengths in the range from 190 nm to 1900 nm, preferably from 700 nm to 900 nm, and even more preferred approximately 810 nm.
At this wavelength the absorption of the light in the hair follicles is lower than at higher wavelengths, and the energy density must therefore be higher than 50 J/cm2, preferably not higher than 150 J/cm2, preferably approximately 100 J/cm2. The time at a specific treatment position, the spot treatment time, may vary from 30-60 ms and to several seconds. In one preferred embodiment of the invention a spot treatment time of 30-100 ms, preferably such as from 50-100 ms, such as approx. 60 ms, is used. But also longer spot treatment times, such as spot treatment times of 30 msxe2x88x923 seconds, such as 50-500 ms, or such as 100 msxe2x88x921 second, such as approx. 250 ms, approx. 500 ms, or such as approx. 1 second, may be used.
It is preferred, that the light source utilised in the present invention is a laser, such as a diode laser, such as a AlGaAs diode laser.
Furthermore, photocoagulation of veins may be obtained by traversing the target surface area stepwise. For example, a single line scan may be performed and the handpiece may be positioned so that the line scan substantially follows the vein to be coagulated. It is preferred to repeat the single line scan so that the vein is traversed by the treating light beam two or three times to ensure proper photocoagulation of the vein. The repeated treatment scans may be performed automatically.
In order to remove hairs from a tissue area, it is important that the power emitted by the light source is absorbed in the hair follicles and its adjacent blood vessels so that the hair follicles are heated to a temperature sufficient to destroy or damage the hair follicles so that the hair dies.
One way of increasing the heating of the hair follicles and the hair duct is disclosed in U.S. Pat. No. 5,925,035, ThermoLase Corporation, wherein a substance, such as a mixture of carbon particles and oil, may be applied to the tissue area to be treated. The substance may then enter the hair duct and light of a wavelength readily absorbed in the substance may illuminate the area to be treated. The power of the light source, preferably a laser, such as a Nd YAG laser, is then chosen so that the carbon particles are heated to a temperature sufficient to devitalise the tissue feeding the hair so that the hair dies, but without heating the surrounding tissue to a temperature which would otherwise induce damages in the surrounding tissue. Other substances or particles may also be applied to the tissue area to be treated, and further the hair may be stained by a dye to increase the absorption of treating light.
Alternatively, to avoid the need for application of light absorbing substances, the tissue area to be treated may be cooled during treatment. It is preferred to cool the tissue area to be treated during treatment whereby the heat is transferred through the upper dermal layers to the hair follicles, heating the hair follicles to a temperature sufficient to damage or destroy the hair follicles whereby regrowth of the hair is at least deferred, and at the same time excessive heating and corresponding damage of the surface tissue is avoided due to the applied cooling.
It is further preferred to cool the entire scan area during treatment and not just the actual spot being treated. Hereby, an effective cooling is achieved before treatment is started, during treatment and after treatment of the specific spot without the need to delay the start of treatment to allow for cooling of the specific spot area before treatment can be started and likewise without the need to await cooling of the spot after the treatment of the spot has been performed. In a preferred embodiment there is only a short delay before and after a complete scan has been performed.
It is to be understood that the application of a substance to increase the absorption of the treating light does not exclude the above-mentioned cooling of the tissue area to be treated.
The cooling of the tissue may be obtained by applying a cooling fluid, such as water, such as a gel, etc. to the surface to be treated during treatment. For example, the fluid may be applied between two plates of a material transparent to the light beams to be used during treatment. The fluid may be positioned in a substantially closed reservoir between the two plates or the reservoir may be provided with an in-let and an out-let whereby the fluid may pass through the reservoir to ensure constant cooling during treatment.
Thus, the apparatus may comprise a cooling member that is adapted to be positioned at the target area for cooling of tissue at the target area and that is at least partly transparent to the first light beam. The cooling member may comprise a frame, an upper window positioned in the frame, and a lower window positioned in the frame, the frame, the upper window, and the lower window defining a volume therebetween for receiving and holding a cooling liquid. Further, the cooling member may comprise an inlet for inputting cooling liquid to the volume and an outlet for outputting cooling liquid from the volume. The cooling member may be attached to the handpiece.
It is preferred to shape the handpiece ergonomically so that a comfortable hand grip is provided for the operator of the apparatus. For example, it is preferred to direct the light beam towards a target area at a substantially right angle to the area. The ergonomic form of the handpiece allows the operator to point the light beam at a substantially right angle to the target surface without having to bend the wrist in an uncomfortable way.
Preferably, the handpiece is light so that it is easy for the operator to hold the handpiece and bring it into any desired position in relation to target surface to be treated. The weight of a preferred handpiece according to the present inventionxe2x80x94cables and fibres not includedxe2x80x94is less than 300 grams, such as 290 grams, or such as 250 grams.
User interface means may be provided for selection of parameters relating to the operation of the handpiece, positioned on the housing of the handpiece.
The parameters may comprise energy density of the output light beam from the handpiece, intensity of the output light beam emitted form the handpiece, size of the target surface area to be traversed by the output light beam, shape of the target surface area to be traversed by the output light beam, etc.
The user interface means may comprise a first button, e.g. a membrane switch, for selection of a parameter type by stepping through a set of parameter types, such as the set listed above or any subset thereof.
The user interface means may further comprise a second button, e.g. a membrane switch, for selection of a parameter value of the parameter type currently selected by stepping through a corresponding set of parameter values. It is envisaged that more values may be selected for a single parameter, the sum of each value selected being the resulting parameter value. Hereby, a wide variety of parameter values is easily obtained from the user interface means.
A set of light emitting diodes may be provided for indication of the set of currently selected parameter values.
It is an important advantage of provision of the user interface at the handpiece that an operation of the handpiece is able to simultaneously select operational parameters of the handpiece and observe resulting changes in treatment effects as the operator is not forced to shift his field of view from the surface area to be treated to a user interface panel positioned somewhere else, e.g. behind the operator.
Preferably, the buttons are positioned on the housing of the handpiece so that single-handed operation is possible, preferably, with the right as well as with the left hand. The user interface means may further comprise a foot pedal. The output beam traverses a target surface area when the operator depresses the pedal. Preferably, output beam traversing is stopped immediately when the operator releases the pedal.
The deflecting means may comprise any optical component or components suitable for deflecting light of the wavelength in question, such as mirrors, prisms, grids, diffractive optical elements, such as holograms, etc, etc.
The deflecting means are preferably movably mounted for displacement of the deflecting means as a function of time, so that the light beam emitted from the handpiece may traverse a surface along a desired curve while the handpiece is kept in a fixed position. Preferably, the deflecting means are rotatably mounted, and the actual deflection of the light beam is determined by the current angular position of the deflecting means.
Moving means may be utilised to control positions of the deflecting means, such as actuators, such as piezo electric crystals, the displacement of which is controlled by applying a specific electric voltage to their electrodes, electromotors generating linear or rotational displacements, galvanometers, magnetically activated or controlled actuators, pneumatic actuators, hydraulic actuators, etc.
The positions of the deflecting means may be controlled by deflecting control means adapted to control the moving means so that the deflecting means deflect the light beam in such a way that it traverses a target surface along a desired curve.
According to a preferred embodiment of the invention, a handpiece is provided, having two mirrors that are rotatably mounted in the path of the light beam in the handpiece. The rotational axis of the mirrors may be substantially perpendicular to each other in order to obtain two dimensional deflection of the light beam.
Alternatively, the movable deflecting means may comprise one mirror that is rotatably around two aces that may be substantially perpendicular to each other.
The moving means for the mirrors may be constituted by electrometors, e.g. each mirror may be directly connected to a shaft of a corresponding motor, whereby each motor is used for angular positioning of the corresponding mirror.
In order to minimise the size of the handpiece, it is preferred to mount the motors with their respective shafts in a common plane. For example, one motor may be a linear motor, such as a linear step motor, generating linear displacements. The shaft on this motor may be connected to the mirror at a first edge of the mirror, while a second and opposite edge of the mirror is rotatably connected to the handpiece. By pushing or pulling the first edge by the linear motor, the mirror is rotated about its rotational axis. The other motor, preferably a galvanometer, may be connected to the other mirror in the conventional way described above, whereby the two mirrors may be rotated around substantially perpendicular axes.
The deflecting control means may be adapted to control the moving means so that the desired curve is a substantially straight line.
Preferably, the deflecting control means are adapted to control the moving means so that the light beam traverses a target surface area line by line.
It is an important advantage of the line by line traversing pattern that areas of any arbitrary shape, such as polygonal, such as rectangular, quadratic, triangular, etc, or circular, elliptic, etc. may be traversed line by line by appropriately controlling the starting point and stopping point of light along each line traversed.
Preferably, the first deflecting control means are adapted to control the first moving means so that the lines are traversed sequentially i.e. neighbouring lines are traversed successively. This minimises the requirement for the operator to be able to keep the handpiece steady in a desired position because when lines are traversed successively, neighbouring lines are traversed within a very short time period so that involuntary hand movements of the operator does not lead to traversing overlap i.e. involuntary hand movements can not within the very short time period during which a single line is traversed move the handpiece back to the line previously traversed which would lead to uneven treatment of the target surface.
If an interlacing traversing pattern were utilised, i.e. every second line of the target surface area is traversed and after that the remaining lines in-between are traversed, there would be sufficient time between traversing of neighbouring lines to allow involuntary movements of the handpiece to a line previously traversed leading to repeated treatment of one area that may damage tissue at that area and leaving another area without treatment.
Thus, according to a third aspect of the invention, a method is provided of traversing a light beam across an area of a tissue for depilating, comprising the steps of emitting the light beam towards the tissue area and illuminating a spot on the target area, deflecting the light beam with movable deflecting means so that the tissue is traversed by the light beam stepwise with steps that are greater than half the diameter of the spot.
The first deflecting control means may be adapted to control the first moving means so that the lines are traversed in the same direction whereby substantially the same amount of power per area is delivered uniformly across the target surface area leading to substantially the same temperature increase at any point of the target surface area after traversing. Alternatively, the first deflecting control means may be adapted to control the first moving means so that the lines are traversed in opposite directions.
When a target area is traversed line by line, it is preferred that movement of one mirror causes the light beam to traverse a line while movement of the other mirror moves the light beam to the next line. In the example above, the galvanometer preferably generates the line traversing as the galvanometer can move the mirror at a high speed, and the linear motor preferably generates the displacement of the light beam to the next line to be traversed.
In order to control positioning of curves on the target area accurately, it is preferred to position the movable deflecting means extremely accurately in the handpiece. In the preferred embodiment of the invention, this is accomplished by utilisation of printed circuit technology providing high accuracies of hole positioning of 0.05 mm. The mirrors are rotated around shafts that are mounted in printed circuit boards providing the required positioning accuracy. Further, the motors rotating the mirrors are also mounted on the printed circuit boards providing electrical connections to the motors and the mechanical support and positioning needed.
When traversing a target surface area line by line, it is preferred to traverse each line in the same direction ensuring uniform heating of cells across the target surface area. Further, it is preferred to provide light switching means for preventing emission of the light beam and light switching control means for controlling the light switching means for turning off the light beam, e.g. by switching off the light source, by inserting a light obstructing member in the light path of the beam, etc, while the light beam is moved from the end of a line having been traversed to the start of the next line to be traversed, in order to avoid repeated illumination of areas of the two lines. Further, the light switching control means may be adapted to control the light switching means for turning off the light beam while the light beam is moved from one spot to the succeeding spot.
Instead of turning the light beam off, the light beam may be moved at a speed significantly larger than the traversing speed or the parameters of the light source emitting the light beam may be controlled (e.g. by lowering the output power of the light source) so that tissue at the target area is not influenced by the light beam, during movement from the end of a line to the start of the next line. When moving the light beam from one spot to a succeeding spot it is preferred to move the light beam at high speed or to control the parameters of the light source as mentioned just above, so that tissue is not influenced when the light beam is moved over an area.
To obtain a fast treatment of large areas of similar tissue types to be treated with substantially the same treatment parameter values, it is preferred that the operator can treat a number of treatment areas without releasing the foot pedal. This facility may be provided by a repeat pattern mode when a delay is inserted after the completion of each treatment scan so as to allow the operator to move the handpiece to a new treatment position where the treatment scan is then repeated. A trained operator may only need a short delay, such as a 1 second delay, but also longer delays, up to 2 or 3 seconds, may be provided. It is preferred that the operator allow the treatment area to cool down just after treatment before the handpiece with the cooling member is removed from treatment area. This may take a few hundred milliseconds.
Typically, the intensity within the beam of a light beam as generated by the light source varies as a normal function of the distance from the centre of the beam. The optical fibre may be designed or selected to be dispersive in such a way that the intensity function of the light beam emitted from the fibre as a function of the distance to the centre of the beam is substantially rectangular, i.e. the intensity of the beam leaving the fibre decays more slowly towards the edge of the beam than the intensity of a beam as generated by the light source whereby heat is more uniformly generated in cells across a traversed line of tissue.
However, when using large spot sizes, such as the spot sizes mentioned above and used with the present invention, the intensity function of the light beam emitted from the fibre is not substantially rectangular, and furthermore due to scattering of the treating light beam at the tissue surface a spot overlap as mentioned above is necessary to obtain a uniform distribution of heat.
A light source generating visible guiding light may be provided for generating a visible guiding light beam that is used to assist the operator by indicating areas towards which the treating light is directed during traversing. For example, the input connector of the handpiece may be further adapted to connect a second beam-outlet end of a second optical fibre for transmission of a visible guiding light beam to the handpiece. The second optical fibre is aligned in the connector along the desired path of the visible light beam. The handpiece may further comprise movable second deflecting means for deflection of the visible guiding light beam in such a way that the treating light beam and the visible guiding light beams emitted from the output of the handpiece illuminate substantially the same area of a target surface.
Preferably, the treating light and the guiding light are transmitted through the same optical fibre and via the same optics so that the spots illuminated by treating light and guiding light, respectively, are substantially identical.
In order to assist the operator of the apparatus in keeping a constant distance from the output of the handpiece to the surface of the tissue to be ablated, the handpiece may comprise a distance member connected to the handpiece at the output with fastening means.
As the distance member will touch the patient, it is desirable to insert a new, disinfected member before treatment of a new patient and thus, it is preferred that the fastening means comprises a magnet so that a used distance member can easily be disconnected from the handpiece, e.g. for autoclaving, and so that a new member can easily be connected to the handpiece.
The handpiece according to the present invention may further comprise a processor for control of the handpiece and comprising one or more control means, such as deflecting control means, light switching control means, means for controlling the light intensity control means, etc. The processor may further be connected to the user interface means and may be adapted to control the functions of the handpiece in accordance with the user interface selections.
Thus, the processor may be adapted to control energy density received by the target surface when traversed by the treating light beam.
The processor may comprise a memory, such as an EEPROM, a flash EEPROM, for storing of different parameters of traversing patterns, such as target surface area size, traversing duration, energy density, etc.
The handpiece may further be provided with a computer interface facilitating reception of traversing pattern parameters generated in a computer and transmitted to the handpiece for storage in the memory. The user interface may be utilised for selection of a specific traversing pattern from the set of patterns stored in the memory as previously described. The computer may be any programmable electronic device capable of storing, retrieving and processing data, such as a PC.
It is an important advantage of provision of a processor in the handpiece that signal lines between the handpiece and an external device controlling the handpiece are not needed. This reduces weight of the handpiece with cables connected. Further, electrical noise on control lines is minimised because of reduced lengths of the lines. Still further, control speed is increased as capacitance of a short line is small.
Various traversing patterns may be created on a PC and be downloaded to the memory of the handpiece. The patterns may stored in the form of a table of parameters defining number of lines, length of lines, distance between lines, start and end points of fade-in and fade-out of each line, points of turn on and turn off of the traversing light beam, etc of each traversing pattern stored.
A traversing pattern box may be provided, containing a processor, a memory and interface means for storage of traversing patterns generated, e.g. on a PC and transmitted to the box through the interface means for storage in the memory. The interface means of the box and the computer interface of a handpiece may be interconnected and the various traversing patterns stored in the box may be transferred to the memory of the handpiece whereby traversing patterns created at a single PC may be distributed to a plurality of handpieces that may be situated remotely from the PC.